btcvar.c

/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*- *//* ***** BEGIN LICENSE BLOCK ***** * Version: MPL 1.1/GPL 2.0/LGPL 2.1 * * The contents of this file are subject to the Mozilla Public License Version * 1.1 (the "License"); you may not use this file except in compliance with * the License. You may obtain a copy of the License at * http://www.mozilla.org/MPL/ * * Software distributed under the License is distributed on an "AS IS" basis, * WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License * for the specific language governing rights and limitations under the * License. * * The Original Code is the Netscape Portable Runtime (NSPR). * * The Initial Developer of the Original Code is * Netscape Communications Corporation. * Portions created by the Initial Developer are Copyright (C) 1998-2000 * the Initial Developer. All Rights Reserved. * * Contributor(s): * * Alternatively, the contents of this file may be used under the terms of * either the GNU General Public License Version 2 or later (the "GPL"), or * the GNU Lesser General Public License Version 2.1 or later (the "LGPL"), * in which case the provisions of the GPL or the LGPL are applicable instead * of those above. If you wish to allow use of your version of this file only * under the terms of either the GPL or the LGPL, and not to allow others to * use your version of this file under the terms of the MPL, indicate your * decision by deleting the provisions above and replace them with the notice * and other provisions required by the GPL or the LGPL. If you do not delete * the provisions above, a recipient may use your version of this file under * the terms of any one of the MPL, the GPL or the LGPL. * * ***** END LICENSE BLOCK ***** */#include <kernel/OS.h>#include "primpl.h"/*** Create a new condition variable.**** "lock" is the lock used to protect the condition variable.**** Condition variables are synchronization objects that threads can use** to wait for some condition to occur.**** This may fail if memory is tight or if some operating system resource** is low. In such cases, a NULL will be returned.*/
PR_IMPLEMENT(PRCondVar*)
PR_NewCondVar (PRLock *lock)
{
PRCondVar *cv = PR_NEW( PRCondVar );
PR_ASSERT( NULL != lock );
if( NULL != cv )
{
cv->lock = lock;
cv->sem = create_sem(0, "CVSem");
cv->handshakeSem = create_sem(0, "CVHandshake");
cv->signalSem = create_sem( 0, "CVSignal");
cv->signalBenCount = 0;
cv->ns = cv->nw = 0;
PR_ASSERT( cv->sem >= B_NO_ERROR );
PR_ASSERT( cv->handshakeSem >= B_NO_ERROR );
PR_ASSERT( cv->signalSem >= B_NO_ERROR );
}
return cv;
} /* PR_NewCondVar *//*** Destroy a condition variable. There must be no thread** waiting on the condvar. The caller is responsible for guaranteeing** that the condvar is no longer in use.***/
PR_IMPLEMENT(void)
PR_DestroyCondVar (PRCondVar *cvar)
{
status_t result = delete_sem( cvar->sem );
PR_ASSERT( result == B_NO_ERROR );
result = delete_sem( cvar->handshakeSem );
PR_ASSERT( result == B_NO_ERROR );
result = delete_sem( cvar->signalSem );
PR_ASSERT( result == B_NO_ERROR );
PR_DELETE( cvar );
}
/*** The thread that waits on a condition is blocked in a "waiting on** condition" state until another thread notifies the condition or a** caller specified amount of time expires. The lock associated with** the condition variable will be released, which must have be held** prior to the call to wait.**** Logically a notified thread is moved from the "waiting on condition"** state and made "ready." When scheduled, it will attempt to reacquire** the lock that it held when wait was called.**** The timeout has two well known values, PR_INTERVAL_NO_TIMEOUT and** PR_INTERVAL_NO_WAIT. The former value requires that a condition be** notified (or the thread interrupted) before it will resume from the** wait. If the timeout has a value of PR_INTERVAL_NO_WAIT, the effect** is to release the lock, possibly causing a rescheduling within the** runtime, then immediately attempting to reacquire the lock and resume.**** Any other value for timeout will cause the thread to be rescheduled** either due to explicit notification or an expired interval. The latter** must be determined by treating time as one part of the monitored data** being protected by the lock and tested explicitly for an expired** interval.**** Returns PR_FAILURE if the caller has not locked the lock associated** with the condition variable or the thread was interrupted (PR_Interrupt()).** The particular reason can be extracted with PR_GetError().*/
PR_IMPLEMENT(PRStatus)
PR_WaitCondVar (PRCondVar *cvar, PRIntervalTime timeout)
{
status_t err;
if( timeout == PR_INTERVAL_NO_WAIT )
{
PR_Unlock( cvar->lock );
PR_Lock( cvar->lock );
return PR_SUCCESS;
}
if( atomic_add( &cvar->signalBenCount, 1 ) > 0 )
{
if (acquire_sem(cvar->signalSem) == B_INTERRUPTED)
{
atomic_add( &cvar->signalBenCount, -1 );
return PR_FAILURE;
}
}
cvar->nw += 1;
if( atomic_add( &cvar->signalBenCount, -1 ) > 1 )
{
release_sem(cvar->signalSem);
}
PR_Unlock( cvar->lock );
if( timeout==PR_INTERVAL_NO_TIMEOUT )
{
err = acquire_sem(cvar->sem);
}
else
{
err = acquire_sem_etc(cvar->sem, 1, B_RELATIVE_TIMEOUT, PR_IntervalToMicroseconds(timeout) );
}
if( atomic_add( &cvar->signalBenCount, 1 ) > 0 )
{
while (acquire_sem(cvar->signalSem) == B_INTERRUPTED);
}
if (cvar->ns > 0)
{
release_sem(cvar->handshakeSem);
cvar->ns -= 1;
}
cvar->nw -= 1;
if( atomic_add( &cvar->signalBenCount, -1 ) > 1 )
{
release_sem(cvar->signalSem);
}
PR_Lock( cvar->lock );
if(err!=B_NO_ERROR)
{
return PR_FAILURE;
}
return PR_SUCCESS;
}
/*** Notify ONE thread that is currently waiting on 'cvar'. Which thread is** dependent on the implementation of the runtime. Common sense would dictate** that all threads waiting on a single condition have identical semantics,** therefore which one gets notified is not significant. **** The calling thead must hold the lock that protects the condition, as** well as the invariants that are tightly bound to the condition, when** notify is called.**** Returns PR_FAILURE if the caller has not locked the lock associated** with the condition variable.*/
PR_IMPLEMENT(PRStatus)
PR_NotifyCondVar (PRCondVar *cvar)
{
status_t err ;
if( atomic_add( &cvar->signalBenCount, 1 ) > 0 )
{
if (acquire_sem(cvar->signalSem) == B_INTERRUPTED)
{
atomic_add( &cvar->signalBenCount, -1 );
return PR_FAILURE;
}
}
if (cvar->nw > cvar->ns)
{
cvar->ns += 1;
release_sem(cvar->sem);
if( atomic_add( &cvar->signalBenCount, -1 ) > 1 )
{
release_sem(cvar->signalSem);
}
while (acquire_sem(cvar->handshakeSem) == B_INTERRUPTED)
{
err = B_INTERRUPTED;
}
}
else
{
if( atomic_add( &cvar->signalBenCount, -1 ) > 1 )
{
release_sem(cvar->signalSem);
}
}
return PR_SUCCESS;
}
/*** Notify all of the threads waiting on the condition variable. The order** that the threads are notified is indeterminant. The lock that protects** the condition must be held.**** Returns PR_FAILURE if the caller has not locked the lock associated** with the condition variable.*/
PR_IMPLEMENT(PRStatus)
PR_NotifyAllCondVar (PRCondVar *cvar)
{
int32 handshakes;
status_t err = B_OK;
if( atomic_add( &cvar->signalBenCount, 1 ) > 0 )
{
if (acquire_sem(cvar->signalSem) == B_INTERRUPTED)
{
atomic_add( &cvar->signalBenCount, -1 );
return PR_FAILURE;
}
}
if (cvar->nw > cvar->ns)
{
handshakes = cvar->nw - cvar->ns;
cvar->ns = cvar->nw;
release_sem_etc(cvar->sem, handshakes, 0);
if( atomic_add( &cvar->signalBenCount, -1 ) > 1 )
{
release_sem(cvar->signalSem);
}
while (acquire_sem_etc(cvar->handshakeSem, handshakes, 0, 0) == B_INTERRUPTED)
{
err = B_INTERRUPTED;
}
}
else
{
if( atomic_add( &cvar->signalBenCount, -1 ) > 1 )
{
release_sem(cvar->signalSem);
}
}
return PR_SUCCESS;
}